The Third Generation Partnership Project (3GPP) has been reviewing self-organizing networks (SON) aimed for promoting the operational efficiency by automatically setting and optimizing various wireless parameters for Long Term Evolution (LTE), which is a next-generation wireless communication standard. Some SON use cases include mobility load balancing (MLB) in which load, such as wireless resources, is balanced between cells by adjusting handover (HO) parameters between adjoining cells.
There is a known method of adjusting handover parameters for MLB. That is, with the known method of adjusting handover parameters for MLB, handover is triggered by comparing the received power measured by a mobile station that is connected to a serving cell and the received power measured by a mobile station that is connected to an adjoining cell. Specifically, when the received power measured by the mobile station from the adjoining cell is larger than the received power from the serving cell by a value exceeding a threshold T, the mobile station is handed over to a target cell, i.e., adjoining cell. At this time, when MLB is carried out on adjoining cells, the threshold associated with the handover trigger is adjusted.
For example, the initial parameter configuration of handing over a mobile station to cell B when the received power from cell B, which is a cell adjoining a serving cell, is larger than the received power from cell A, which is the serving cell, by a threshold, i.e., 3 dB, is considered. At this time, if the load on cell A is higher than the load on cell B, MLB is carried out, and the threshold is set to, for example, 1 dB. By setting a small threshold, the area covered by cell A decreases and the area covered by cell B increases, promoting handover of the mobile station from cell A to cell B. At the same time, the handover threshold of the mobile station for cell A is updated in cell B. In such a case, in cell B, the large threshold of the received power measured by the mobile station from cell A is set to prevent the mobile station from being handed over from cell B to cell A.
Examples of the related art include: 3GPP TR 36.902 V9.2.0; and R. Nasri and Z. Altman, Handover adaptation for dynamic load balancing in 3GPP long term evolution systems, 5th Int. Conf. on Advanced in Mobile Computing Multimedia (MoMM2007), Jakarta, Indonesia, December 2007.